Pneumonia is one of the leading causes of hospitalization of children. Many children hospitalized with pneumonia develop complications, including parapneumonic effusion or empyema. Imaging by either ultrasound (US) or computed tomography (CT) plays a pivotal role in treatment decisions. While published national guidelines recommend use of US (which avoids the risks of radiation exposure), many hospitalized children with pneumonia nevertheless undergo CT. I theorize that this divergence existed due to the under-utilization of clinical practice pathways to guide the care of pediatric patients with pneumonia, and concerns that CT is superior to US in the management of these patients. Objective: This project seeks to understand why, and to identify means to remedy the overuse of CT. In particular, the project focuses on whether and how hospitals use (or do not use) clinical practice pathways to guide the care of hospitalized pediatric pneumonia patients, and on the safety of US compared to CT as the primary imagining modality of these patients. Specific Aim 1: To test whether hospitals with a higher proportion of US have, compared to hospitals with a higher proportion of CT, equivalent post-imaging effusion management procedures, Length of Stay (LOS), mortality, and readmissions for children with pneumonia, adjusting for case mix. Specific Aim 2: To test whether hospitals with higher quality pneumonia imaging pathways use US more commonly than CT compared to hospitals without such pathways in children with pneumonia, adjusting for patient characteristics and severity of illness on the first day of hospitalization. Relevance: Consistent with AHRQ's aim to identify strategies for practice improvement, to improve quality of care, and to enhance patient safety, this proposal will provide valuable information about the role of hospital-level clinical pathways that promote uptake and acceptance of national guidelines to foster evidence-based practice and limit radiation exposure in children. Methods: I will use data from the Pediatric Health Information System (PHIS), a clinically detailed administrative dataset of children's hospitals in the United States, and a smaller PHIS-based dataset that has been augmented by chart review of pediatric inpatients with complicated pneumonia. I will survey PHIS hospitals on their use of clinical practice pathways. Research Training Program: The proposed project is part of a larger training and educational agenda developed to prepare me for a productive career as an independent health services researcher. In addition to the proposed project, I will complete advanced coursework in epidemiology and quality improvement methods while receiving close mentorship from successful investigators.